1. Field
The present disclosure relates to a power control system for a plurality of energy storage devices and a control device and control method thereof, and more particularly, to a power control system and method for controlling the charging and discharging of a plurality of energy storage devices connected to a new renewable energy source, a power system or the like.
2. Discussion of Related Art
In response to a rapid increase in the price of petroleum and natural gas, the power industry is expected to significantly and quickly change in terms of its structure, operation, planning, and regulation. Recently, a smart grid is introduced for power suppliers or system operators and consumers to optimize energy efficiency through a bi-directional exchange of power usage information in real-time by a combination of a power network and a communication network.
In a smart grid, independent management and operation are performed by introducing distributed power that is based on new renewable energy. Also, the inefficiency of conventional power systems may be solved by providing services that are based on intellectualization and several other techniques to respond to the demand of consumers in real-time.
The smart grid has evolved into a power control system including an energy storage device in order to store surplus power when the amount of energy generated is large and supply power when the amount of energy generated is small.
In association with this, FIG. 1 is a schematic block diagram of a power control system for a plurality of energy storage devices according to the related art. For reference, FIG. 1 shows a structure in which two energy storage devices 30 and 40 are connected between a first power system 10 and a second power system 20.
In the related art, when the energy storage devices are connected, respective direct current-to-direct current (DC-DC) converters are used. The power of the individual energy storage devices is adjusted by adjusting the voltage of each of the DC-DC converters.
Referring to FIG. 1, the first power system 10 is connected with a direct current (DC) linker 50 through a first converter 15, and the second power system 20 is connected with the DC linker 50 through a second converter 25. A control device 60 controls a voltage of the DC linker 50 by controlling a voltage V1 of the first converter 15 on the basis of power P1 of the first converter 15 and by controlling a voltage V2 of the second converter 25 on the basis of power P2 of the second converter 25.
A first energy storage device 30 is connected to the DC linker 50 through a first DC-DC converter 35. Also, a second energy storage device 40 is connected to the DC linker 50 through a second DC-DC converter 45. Here, each of the energy storage devices 30 and 40 has a voltage that is substantially fixed due to its chemical properties. The voltage varies slightly depending on a state of charge (SOC). Therefore, the first DC-DC converter 35 controls a low-voltage side DC voltage V3b to maintain a voltage V3a which the first energy storage device 30 requires, and the second DC-DC converter 45 likewise controls a low-voltage side DC voltage V4b to maintain a voltage V4a which the second energy storage device 40 requires.
As described above, power control is performed using respective DC-DC converters of the energy storage devices, and thus a number of DC-DC converters equal to the number of energy storage devices are needed. Whenever one DC-DC converter is additionally installed, the cost increases, and the efficiency decreases due to power loss. Accordingly, a solution is required to reduce the number of DC-DC converters to decrease the cost and increase the efficiency.